Monosaccharides
(simple sugars) have a carbon skeleton of 3 or more carbons depending
on the monosaccharide. The most familiar monosaccharide is Glucose
(C6 H12 O6). A ball and stick model of glucose is shown here in
its ring form, which is the form it takes in water. As a solid, glucose
has a straight chain form which is not shown.

Disaccharides.
Disaccharides consist of two monosaccharides linked
together by a dehydration synthesis.

Sucrose is common disaccharide
which functions as a transport sugar in plants. The production of sucrose
by means of a dehydration synthesis is shown here. Each sucrose molecule
is made by chemically combining a glucose and a fructose molecule.

A hydrogen is removed from the glucose and a hydroxyl(OH)
from the fructose leaving an oxygen to link the two molecules together.

Lactose, another disaccharide,
is commonly called milk sugar.

This diagram shows the synthesis of sucrose from glucose and fructose
via a dehydration synthesis.

Oligosaccharides:
Oligo means a few and oligosaccharides have a few simple sugars linked together
but not thousands as do polysacchardes. Oligosacharides are common on cell
membranes and surfaces where they often serve as cell markers.

Polysaccharides:
Polysaccharides are the most abundant organic compounds
in the biosphere. The most commonly seen polysaccharide is cellulose and
scientist estimate that over one trillion tons of cellulose are synthesized
by plants each year. Cellulose forms the cell wall of plants.

Starches can be digested by animals but cellulose cannot.
Most animals that injest grass or wood have special micro organisms living
in their gut that digest the cellulose and the animals in turn absorp
the breakdown product

This diagram compares the way the glucose units bond in starch versus
cellulose. What differences do you observe? These differences are largely
responsible for the quite different properties of starches and cellulose.

Amylopectin:Some starches such as amylopectin are branched and this gives
the starch a jelly-like appearence. Pectin is one such starch that is produced
by apples and used to thicken jellies.

Even though we typically associate starch as being made
by plants, many animals produce a highly branched starch like compound
called glycogen. In mammals glycogen is stored
in the liver and the muscles where it provides a quick source of energy
and serves as a storage substance for excess glucose taken up from the
blood.